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Abstract:

A distribution of an element to improve coercivity for each magnet is
decided, based on analysis results of magnetic fields within a plurality
of magnets (M26 and the like), and by structuring each of the
plurality of magnets based on the distribution, it becomes possible to
realize a permanent magnet having strong magnetic force and high
heat-resisting performance whose residual magnetic flux density and
coercivity are both improved, using a small amount of an element which
improves coercivity. And, by designing a magnet unit using the permanent
magnet, and a motor using the magnet unit, it becomes possible to obtain
a motor with high performance.

Claims:

1-24. (canceled)

25. A design method of a motor which is structured using a magnet unit
including a plurality of magnets and a coil unit including a plurality of
coils, the method comprising: deciding a distribution of an element which
improves coercivity inside the plurality of magnets for each of the
plurality of magnets, based on results of an analysis performed of a
magnetic field induced by the plurality of magnets included in the magnet
unit arranged corresponding to the coil unit; and designing the magnet
unit using the plurality of magnets which are each structured based on
the distribution of the element which improves the coercivity.

26. The design method of a motor according to claim 25 wherein in the
deciding, the distribution of the element which improves the coercivity
is decided from a distribution of an area whose intensity of the magnetic
field inside each of the plurality of magnets is smaller than a threshold
value.

27. The design method of a motor according to claim 26 wherein the
distribution of the element which improves the coercivity is decided so
that the area whose intensity of the magnetic field in each of the
plurality of magnets is smaller than the threshold value contains more of
the element which improves the coercivity than an area whose intensity of
the magnetic field is larger than the threshold value.

28. The design method of a motor according to claim 26 wherein a
distribution of an added element different from the element which
improves the coercivity is decided so that an area whose intensity of the
magnetic field in each of the plurality of magnets is larger than the
threshold value contains more of the added element than the area whose
intensity of the magnetic field is smaller than the threshold value.

29. The design method of a motor according to claim 26 wherein the
threshold value is decided from at least one of a direction of a magnetic
pole, a residual magnetic flux density and the coercivity of each of the
plurality of magnets.

30. The design method of a motor according to claim 26 wherein the
threshold value is given from a magnetic flux density at a maximum
inflection point of a demagnetizing curve for each of the plurality of
magnets.

31. The design method of a motor according to claim 25 wherein the
plurality of magnets are arranged to structure a magnetic flux density
distribution that corresponds to a placement of a plurality of coils
included in the coil unit on a reference plane of the coil unit.

32. The design method of a motor according to claim 25 wherein in the
designing, the plurality of magnets which are structured by partially
adding the element to improve the coercivity are used, based on the
distribution of the element which improves the coercivity.

33. The design method of a motor according to claim 25 wherein each of
the plurality of magnets is a rare earth-containing magnet which contains
at least Nd2Fe14B, and the element which improves the
coercivity is dysprosium.

34. The design method of a motor according to claim 25 wherein the motor
is a linear motor in which one of the magnet unit and the coil unit
serves as a mover and the other serves as a stator, and the mover moves
in a uniaxial direction with respect to the stator.

35. A manufacturing method of a motor, comprising: designing a motor
using the design method of a motor according to claim 25; and
manufacturing the motor according to results of the designing.

36. A motor which is designed using the design method of a motor
according to claim 25, and is manufactured according to results of the
design.

37. A motor which is structured using a magnet unit including a plurality
of magnets and a coil unit including a plurality of coils, wherein the
magnet unit is designed using the plurality of magnets which are each
structured based on a distribution of an element which improves
coercivity inside the plurality of magnets for each of the plurality of
magnets, the distribution being decided based on results of analyzing a
magnetic field induced by the plurality of magnets included in the magnet
unit arranged corresponding to the coil unit.

38. The motor according to claim 37 wherein the distribution of the
element which improves the coercivity is decided from a distribution of
an area whose intensity of the magnetic field inside each of the
plurality of magnets is smaller than a threshold value.

39. The motor according to claim 38 wherein the distribution of the
element which improves the coercivity is decided so that the area whose
intensity of the magnetic field in each of the plurality of magnets is
smaller than the threshold value contains more of the element which
improves the coercivity than an area whose intensity of the magnetic
field is larger than the threshold value.

40. The motor according to claim 38 wherein a distribution of an added
element different from the element which improves the coercivity is
decided so that an area whose intensity of the magnetic field in each of
the plurality of magnets is larger than the threshold value contains more
of the added element than the area whose intensity of the magnetic field
is smaller than the threshold value.

41. The motor according to claim 38 wherein the threshold value is
decided from at least one of a direction of a magnetic pole, a residual
magnetic flux density and the coercivity of each of the plurality of
magnets.

42. The motor according to claim 38 wherein the threshold value is given
from a magnetic flux density at a maximum inflection point of a
demagnetizing curve for each of the plurality of magnets.

43. The motor according to claim 37 wherein the plurality of magnets are
arranged to structure a magnetic flux density distribution that
corresponds to a placement of a plurality of coils included in the coil
unit on a reference plane of the coil unit.

44. The motor according to claim 37 wherein the plurality of magnets
which are structured by partially adding the element to improve the
coercivity are used, based on the distribution of the element which
improves the coercivity.

45. The motor according to claim 37 wherein the plurality of magnets are
each a rare earth-containing magnet which contains at least
Nd2Fe14B, and the element which improves the coercivity is
dysprosium.

46. The motor according to claim 37 wherein the motor is a linear motor
in which one of the magnet unit and the coil unit serves as a mover and
the other serves as a stator, and the mover moves in a uniaxial direction
with respect to the stator.

47. A stage device, comprising: the motor according to claim 46; a stage
support member in which one of the magnet unit and the coil unit
structuring the motor is provided; and a stage in which the other of the
magnet unit and the coil unit is provided, and is supported by the stage
support member.

48. An exposure apparatus which transfers a pattern formed on a mask onto
an object, the apparatus comprising: the stage device according to claim
47 serving as a moving device of at least one of the mask and the object.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This non-provisional application claims the benefit of Provisional
Application No. 61/489,078 filed May 23, 2011, the disclosure of which is
hereby incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to motors, design methods and
manufacturing methods of motors, stage devices, and exposure apparatuses,
and more particularly, to a motor structured using a magnet unit
including a plurality of magnets and a coil unit including a plurality of
coils, a design method and a manufacturing method of the motor, a stage
device provided with the motor, and an exposure apparatus provided with
the stage device.

[0004] 2. Description of the Background Art

[0005] As a driving source of magnetic levitation trains,
electrically-powered cars, hybrid cars, machine tools, movable stages of
exposure apparatuses and the like, motors and the like which generate a
force through the interaction of a magnetic field and an electric current
are used, such as a linear motor to obtain a linear motion, a rotary
motor to obtain a rotational motion, and also a planar motor to obtain a
planar motion. These motors are structured so that one of a magnet unit
including a plurality of permanent magnets and a coil unit including a
plurality of coils serves as a mover (or a rotor) while the other serves
as a stator, and the mover is driven in a uniaxial direction, a rotation
direction, or a planar direction with respect to the stator.

[0006] Performance of the motors described above depends heavily on the
properties of the permanent magnets. Properties used to describe the
permanent magnets are, for example, residual magnetic flux density Br,
coercivity Hc, BH product (or maximum energy product BHmax) and the
like. Here, residual magnetic flux density Br is the magnetic flux
density remaining when the intensity of the magnetic field in a
hysteresis curve (demagnetizing curve) becomes zero, and coercivity Hc is
the intensity of the demagnetization field required to reduce the
magnetic flux density to zero.

[0007] Making a strong permanent magnet requires high residual magnetic
flux density Br and high coercivity Hc (and also high BHmax). Since
the intensity of a magnet is proportional to the magnetic flux density, a
magnet with higher residual magnetic flux density Br makes a stronger
magnet. Furthermore, a magnet with higher coercivity Hc can continue to
maintain higher magnetic force in a stable manner.

[0008] As strong permanent magnets used in motors, rare earth-containing
magnets are promising. Representing such magnets are; samarium-cobalt
magnet (Sm2Co17); neodymium iron boron magnet
(Nd2Fe14B), and the like. These magnets, however, possess
properties of demagnetizing under a high temperature environment.
Therefore, to increase coercivity Hc, for example, dysprosium Dy can be
added (for example, refer to U.S. Patent Application Publication No.
2008/0245442). With dysprosium Dy, however, there is a problem of
dysprosium being expensive, with prices being unstable. Further, by
adding dysprosium Dy, residual magnetic flux density Br decreases.
Therefore, it was difficult to increase both residual magnetic flux
density Br and coercivity Hc (also, BHmax) using only a small amount
of dysprosium Dy.

SUMMARY OF THE INVENTION

[0009] The present invention was made under the circumstances described
above, and from a first aspect, the present invention is a design method
of a motor which is structured using a magnet unit including a plurality
of magnets and a coil unit including a plurality of coils, the method
comprising: deciding a distribution of an element which improves
coercivity inside the plurality of magnets for each of the plurality of
magnets, based on results of an analysis performed of a magnetic field
induced by the plurality of magnets included in the magnet unit arranged
corresponding to the coil unit; and designing the magnet unit using the
plurality of magnets which are each structured based on the distribution
of the element which improves the coercivity.

[0010] According to this method, the distribution of the element which
improves coercivity for each of the plurality of magnets is decided,
based on results of the analysis of magnetic fields within the plurality
of magnets, and the plurality of magnets are each structured based on the
distribution. This allows a permanent magnet having strong magnetic force
and high heat-resisting performance whose residual magnetic flux density
and coercivity are both improved to be realized, using a small amount of
an element which improves coercivity. And, by designing a magnet unit
using the permanent magnet, and a motor using the magnet unit, it becomes
possible to improve the performance of the motor.

[0011] From a second aspect, the present invention is a manufacturing
method of a motor, comprising: designing a motor using the design method
of a motor of the present invention; and manufacturing the motor
according to results of the designing.

[0012] According to this method, a motor having a large driving force can
be manufactured.

[0013] From a third aspect, the present invention is a first motor which
is designed using the design method of a motor of the present invention,
and is manufactured according to results of the design.

[0014] According to this motor, a motor having a large driving force can
be obtained.

[0015] From a fourth aspect, the present invention is a second motor which
is structured using a magnet unit including a plurality of magnets and a
coil unit including a plurality of coils, wherein the magnet unit is
designed using the plurality of magnets which are each structured based
on a distribution of an element which improves coercivity inside the
plurality of magnets for each of the plurality of magnets, the
distribution being decided based on results of analyzing a magnetic field
induced by the plurality of magnets included in the magnet unit arranged
corresponding to the coil unit.

[0016] According to this motor, the distribution of the element which
improves coercivity for each of the plurality of magnets is decided,
based on results of the analysis of magnetic fields within the plurality
of magnets, and the plurality of magnets are each structured based on the
distribution. This allows a permanent magnet having strong magnetic force
and high heat-resisting performance whose residual magnetic flux density
and coercivity are both improved to be realized, using a small amount of
an element which improves coercivity. And, by designing a magnet unit
using the permanent magnet, and a motor using the magnet unit, it becomes
possible to improve the performance of the motor.

[0017] From a fifth aspect, the present invention is a stage device,
comprising: the second motor of the present invention; a stage support
member in which one of the magnet unit and the coil unit structuring the
motor is provided; and a stage in which the other of the magnet unit and
the coil unit is provided, and is supported by the stage support member.

[0018] According to this stage device, a stage device which can perform a
high speed drive can be obtained.

[0019] From a sixth aspect, the present invention is an exposure apparatus
which transfers a pattern formed on a mask onto an object, the apparatus
comprising: the stage device of the present invention serving as a moving
device of at least one of the mask and the object.

[0020] According to this apparatus, an exposure apparatus having a high
throughput that drives at least one of a mask and an object at a high
speed can be obtained.

BRIEF DESCRIPTION OF DRAWINGS

[0021] In the accompanying drawings;

[0022] FIG. 1A is a perspective view indicating an external appearance of
a linear motor related to an embodiment, and FIG. 1B is an XY sectional
view of the linear motor;

[0023] FIG. 2A is an enlarged view of a YZ cross-section of the linear
motor, and FIG. 2B is a view showing an arrangement and directions of
magnetic poles of permanent magnets included in a mover (magnet unit);

[0024] FIG. 3A is a view showing an arrangement of permanent magnets
within a magnet unit, FIG. 3B is a view showing a magnetic flux density
distribution within the permanent magnets in the magnet unit obtained by
a magnetic field analysis, and FIG. 3c is an enlarged view showing
ellipse C in FIGS. 3A and 3B;

[0025] FIGS. 4A and 4B are views showing results of demagnetization
evaluation of the permanent magnets;

[0026] FIG. 5 is a chart showing results on performance evaluation of the
linear motor;

[0027] FIG. 6 is a perspective view showing a schematic structure of an
exposure apparatus of an embodiment; and

[0028]FIG. 7 is a perspective view showing a schematic structure of a
reticle stage device.

DESCRIPTION OF TH EMBODIMENTS

[0029] Hereinafter, an embodiment of the present invention will be
described, using FIGS. 1 to 7.

[0030] FIG. 1A is a perspective view showing an external appearance of a
linear motor 80 related to the present embodiment, and FIG. 18 is an XY
sectional view of a schematic structure of linear motor 80. Linear motor
80 is a moving-magnet type linear motor which employs a driving method
using the Lorentz force (electromagnetic force). Linear motor 80 is
structured from a stator (hereinafter indicated using the same numerical
references as coil unit 80A) consisting of a plate shaped coil unit 80A
whose longitudinal direction is the driving direction (X-axis direction
in this case), and a mover (hereinafter indicated using the same
numerical references as magnet units 80B1 and 80B2) consisting
of magnet units 80B1 and 80B2 which are placed on both the
front and rear surfaces (+-Y sides) of stator 80A.

[0031] FIG. 2A shows a concrete structure of linear motor 80. Coil unit
80A includes 14 coils (five U-phase coils, five V-phase coils, and four
W-phase coils) which make up a three-phase coil. FIG. 2A shows eight
coils; U2, V2, W2, U3, V3, W3, U4, and V4. These coils are arranged
spaced constantly apart in the X-axis direction inside a base 80A0
which is made of a nonmagnetic body.

[0032] As shown in FIG. 2B, magnet unit 80B1 includes 40 permanent
magnets (hereinafter, simply called magnets) Mij (i=1 to 5, j=1 to
8), arranged in the X-axis direction on a yoke member 80B10. As
magnet Mij, a rare earth-containing magnet is employ such as, for
example, neodymium iron boron magnet (Nd2Fe14B). Further, as
yoke member 80B10, a magnetic body is employed which has high
permeability and large saturation magnetization. Incidentally, the magnet
unit can be configured, for example, by preparing 40 magnets
individually, or by dividing one magnet into 40 areas according to the
directions of the magnetic poles.

[0033] In magnet Mij, 8 magnets (for example, magnets M21,
M22, M23, M24, M25, M26, M27, and M28)
whose directions of the magnetic poles within an XY plane and widths in
the X-axis direction are different serve as a unit (unit MU2), which is
classified into one of five units MU1 to MU5. FIGS. 2A and 2B show
magnets which are facing 8 coils U2, V2, W2, U3, V3, W3, U4, and V4
within coil unit 80A.

[0034] Magnet unit 80B2 is also configured in a similar manner as
magnet unit 80B1. However, magnet unit 80B2 is placed so that
the directions of the magnetic poles of the magnets within magnet unit
80B2 are opposite to the directions of the magnetic poles of the
magnets within magnet unit 80B1, with the center (reference line Lc)
of coil unit 80A serving as a reference.

[0035] The arrangement of the magnets in magnet units 80B1 and
80B2, or more specifically, the directions of the magnetic poles in
the XY plane and the widths in the X-axis direction of the magnets are
decided so that a magnetic field (magnetic flux density) with a
sinusoidal distribution is induced on the center (reference line Lc) of
coil unit 80A. In FIG. 2B, the directions of the magnetic poles of each
magnet (directions from S-pole to N-pole) are indicated using arrows. The
directions of the magnetic poles are shifted by an angle of 45 degrees
with respect to the directions of the magnetic poles of adjacent magnets.
For example, the directions of the magnetic poles of magnets M21,
M22, M23, M24, M25, M26, M27, and M26
in unit MU2 rotate in sequence at an angle of -45 degrees, and the
direction of the magnetic pole of magnet M31 in unit MU3 adjacent to
unit MU2 becomes the same as the direction of the magnetic pole of magnet
M21.

[0036] However, the angle shifted of the directions of the magnetic poles
is not limited to 45 degrees. For example, a structure can be employed of
rotating the directions of the magnetic poles by increasing the number of
magnets to make the angle to be shifted smaller than 45 degrees. Further,
the angle to be shifted can be set as required so that the directions of
the magnetic poles return in the end to the original angle in one unit,
without making the angle to be shifted equal between all the magnets.

[0037] The widths of the magnets in the X-axis direction are set so that
magnets whose directions of the magnetic poles are in the Y-axis
direction have larger widths than those of magnets whose directions of
the magnetic poles are in other directions. For example, as for unit MU2,
the widths of magnets M24 and M20 are larger than the widths of
other magnets M21, M22, M23, M25, M26, and
M27. The width of a unit in the X-axis direction is decided so that
to an array pitch of one U-phase coil, V-phase coil, and W-phase coil
each, two units of magnets are arranged. However, the widths of the
magnets in the X-axis direction are not limited to these structures, and
can be appropriately set.

[0038] A design method of a motor of the present invention will be
described, using linear motor 80 described above as an example.

[0039] In a first step, linear motor 80, especially magnet units 80B1
and 80B2 (and coil unit 80A) included in linear motor 80 are
designed. As previously described, corresponding to the structure
(arrangement of coils and the like) of coil unit 80A, the arrangement of
magnets Mij (i=1 to 5, j=11 to 8) on yoke members 80B10 and
80B20 inside magnet units 80B1 and 80B2, namely, the
directions of the magnetic poles, the width and the like of each magnet,
are decided so as to induce a magnetic field of a predetermined magnetic
flux density distribution on reference line Lc (for example, a position
where coil unit 80A is located at the time of driving). According to this
arrangement, magnet units 80B1 and 80B2 are designed, as shown
in FIG. 3A.

[0040] In a second step, a magnetic field is analyzed, which is induced by
magnets Mij in magnet units 80B1 and 80B2 designed in the
manner described above, or namely, in a magnetic circuit structured by
magnets Mij (i=1 to 5, j=1 to 8), yoke members 80B10 and
80B20, and the like. For the analysis, for example, an
electromagnetic field analysis using a finite element method can be
employed. Further, in the analysis, adding to the placement and the like
of magnets Mij and yoke members 80B10 and 80B20 decided
above, properties of each magnet such as residual magnetic flux density,
coercivity, permeability and the like determined by the composition of
the magnets, permeability (furthermore, dependence of the permeability on
the intensity of the magnetic field) of the yoke members and the like are
considered.

[0041] From magnetization I and intensity of magnetic field H that each
magnet has, a magnetic field (magnetic flux density) B induced by magnets
Mij is given, as B=I+μH. Here, coefficient μ is permeability.
Inside the magnets, because magnetization I itself induces a
demagnetizing field Hd(>0), magnetic flux density B becomes smaller
than magnetization I only by an amount of the magnetic flux density
occurring due to demagnetizing field Hd. Further, because magnetic fields
induced by magnetization of adjacent magnets and magnetization of yoke
members 80B10 and 80B20 act as a demagnetized field (magnetized
field), magnetic flux density B becomes smaller (or larger).

[0042] According to the magnetic field analysis described above, the
magnetic field (magnetic flux density distribution) inside the magnets is
obtained, as shown in FIG. 3B. FIG. 3c shows an enlarged view of the
magnetic flux density distributions inside magnets M23, M24,
M25, M26, M27, M28, and M31 indicated by an
ellipse C in FIGS. 3A and 3B. In an area ELB inside the magnets,
such as for example, the -Y section of magnet M24 whose direction of
the magnetic pole is in the +Y direction, the vicinity of the border with
magnet M24 of magnets M23 and M25 positioned on both sides
of magnet M24, the +Y section of magnet M26 whose direction of
the magnetic pole is in the -X direction, the -Y section of magnet
M29 whose direction of the magnetic pole is in the -Y direction, and
the vicinity of the border with magnet M28 of magnets M27 and
M31 positioned on both sides of magnet M28, it can be seen that
the magnetic field is weaker (magnetic flux density is lower) than other
areas.

[0043] In the above analysis results, this means that in area ELB
where the magnetic field is weak, the demagnetizing field induced by the
magnetization that each magnet has, the magnetic field generated by the
adjacent/opposing magnets, or the demagnetized field (to be collectively
called a demagnetized field) induced by the yoke member (or the space
formed with coil unit 80A) is strong. When intensity H' of such
demagnetized field is larger than coercivity Hc of each magnet
(H'>Hc), the magnet is demagnetized, which decreases its function as a
magnet. Accordingly, H'>Hd is to be obtained so that magnets
Mij(i=1 to 5, j=1 to 8) serve as magnets structuring magnet units
80B1 and 80B2. Meanwhile, as for other areas having a strong
magnetic field, this means that demagnetization field H' is weak. In such
areas, even if coercivity Hc is somewhat smaller, the magnet is not
demagnetized. Accordingly, only in area ELB within magnets Mij
(i=1 to 5, j=1 to 8) where the magnetic field is weak, coercivity Hc
higher than the other areas having a stronger magnetic field becomes
necessary.

[0044] To obtain higher coercivity Hc, an element to increase coercivity
Hc can be added to the rare earth-containing magnet, which is the
neodymium iron boron magnet (Nd2Fe14B) as previously described.
Here, dysprosium Dy will be chosen. This allows high coercivity Hc, and
will also make demagnetization difficult under an environment of high
temperature. However, there is a problem of dysprosium Dy being
expensive, and having an unstable cost. Further, adding dysprosium Dy
causes a decrease in residual magnetic flux density Br.

[0045] Therefore, in a third step, based on the above analysis results,
addition distribution of dysprosium Dy is decided so that dysprosium Dy
is added only in area (the area having a strong demagnetized field)
ELB having a weak magnetic field within the magnet, or a relatively
higher amount of dysprosium Dy is added to area ELB than the other
areas. Here, the addition distribution is decided to be equal to area
ELB. This allows high coercivity Hc to be obtained in area ELB,
and in the other areas, residual magnetic flux density Br is maintained
strongly. Accordingly, in the individual magnets considered as a whole,
both the residual magnetic flux density and coercivity are improved using
a small amount of dysprosium Dy, and a magnet having strong magnetic
force and high heat-resisting performance can be obtained.

[0046] Further, along with deciding the addition distribution of an
element to improve coercivity Hc, for example, a distribution of adding
an element to improve residual magnetic flux density Br, or a
distribution of adding an element to improve heat-resisting performance
can also be decided. In such a case, because priority is given to adding
elements that improve coercivity Hc, these distributions should be
decided so that the elements are added to areas other than area ELB,
relatively more than the amount added to area ELB.

[0047] Incidentally, in the second step, while the area where the magnetic
field is weaker than a predetermined threshold value (the magnetic flux
density is lower than the threshold value) is obtained as area ELB,
in the third step, in order to obtain high residual magnetic flux density
and high coercivity using a small amount of dysprosium Dy, the threshold
value has to be appropriately selected based on the placement of each
magnet, that is, the directions of the magnetic poles, residual magnetic
flux density, coercivity and the like. As an example, the threshold value
is preferably given with a magnetic flux density at the maximum
inflection point of a demagnetizing curve for each magnet, an average of
the magnetic flux density inside each magnet and the like, serving as a
reference. Further, in the present embodiment, while only one threshold
value was set, the threshold value is not limited to this. For example, a
plurality of threshold values can be set based on the magnitude of the
magnetic flux density of the magnets, and the amount of dysprosium Dy
added, the distribution state of dysprosium Dy, or both the amount and
the distribution state can be decided according to each threshold value.

[0048] In a fourth step, dysprosium Dy is added based on the distribution
of addition obtained above, and magnets Mij (i=1 to 5, j=1 to 8) are
each structured. As shown in FIG. 3c, here, area ELB is in contact
with a part of the border of the magnets. Therefore, for example, by
applying dysprosium oxide, dysprosium fluoride, or an alloy powder
containing dysprosium to the surface of the part of the border of the
magnets and performing a high-temperature processing to diffuse
dysprosium Dy inside the magnets, dysprosium Dy can be added restricting
the area to area ELB. Incidentally, details on addition of elements
such as dysprosium Dy and the like are disclosed, for example, in Kokai
(Japanese Unexamined Patent Application Publication) No. 2010-135529 (the
corresponding U.S. Patent Application Publication No. 2011/0210810).

[0049] Magnet units 80B1 and 80B2 are designed using magnets
Mij (i=1 to 5, j=1 to 8) structured in the manner described above,
and linear motor 80 is structure using magnet units 80B1 and
80B2.

[0050] Here, the arrangement (of the directions of the magnetic poles,
width and the like of each magnet) of magnets Mij (i=1 to 5, j=1 to
8) within magnet units 80B1 and 80B2 can be decided again
(perform step 1), and then steps 2, 3, and 4 can be repeatedly performed.
This makes it possible to design linear motor 80 which has a more
suitable structure.

[0051] Demagnetization properties were evaluated of a magnet structured in
the manner described. The evaluation results are indicated in FIGS. 4A
and 4B. While it can be seen from FIG. 4A that demagnetization occurs at
a temperature equal to or higher than room temperature (of around 20
degrees) in the magnet without dysprosium Dy added, demagnetization does
not occur until around 60 degrees in the magnet (developed product) of
the present embodiment. Incidentally, the temperature of 60 degrees is
the upper limit of the environmental temperature in which the linear
motors are used in exposure apparatus 10 that will be described later on.
Further, from FIG. 4B, while it can be seen that the magnet to which
dysprosium Dy has been added entirely shows the same demagnetization
properties as the demagnetization properties of the magnet of the present
embodiment, the magnetic force is weak. Accordingly, it can be seen that
a magnet having strong magnetic force and high heat-resisting performance
has been obtained by effectively improving both the residual magnetic
flux density and coercivity using a small amount of dysprosium Dy.

[0052] When the design of the present embodiment is used, because
dysprosium Dy is diffused locally and selectively, and is not diffused
evenly throughout the magnets Mij (i=1 to 5, J=1 to 8), the amount
of dysprosium Dy added can be reduced. In this case, in each magnet, it
can be said that the positional relation between the direction of the
magnetic flux and the area where dysprosium Dy is distributed differs
depending on which section the magnet is placed in the magnetic circuit.
For example, as for magnet M24 in magnet unit 80B1, when the
direction of the magnetic pole is in a first direction (in this case, -Y
direction), dysprosium Dy is distributed in an area where dysprosium Dy
is in a first state with respect to the first direction (distributed on
the tip side of the arrow indicating the magnetic pole direction),
whereas, regarding magnet 28, when the direction of the magnetic pole is
in a second direction (in this case, +Y direction), dysprosium Dy is
distributed in an area where dysprosium Dy is in a second state different
from the first state with respect to the second direction (distributed on
the rear end side of the arrow indicating the magnetic pole direction).

[0053] Incidentally, in the above embodiment, while the distribution of
area ELB was obtained for all of the magnets Mij (i=1 to 5, j=1
to 8), and dysprosium Dy was added selectively in the areas, the present
embodiment is not limited to this structure. For example, when the design
method of the present embodiment is applied only to magnets (areas)
having magnetic poles in one predetermined direction in one unit of MU1
to MU5, a similar effect can be obtained at least regarding such magnets.

[0054] Evaluation was performed of the performance of linear motor 80
designed and manufactured using the magnet described above. FIG. 5 shows
evaluation results concerning two prototypes (No. 1 and No. 2) and a
current model. In the two prototypes, compared to the current model,
magnetic flux density was improved by 4.0% and 2.5% (not shown), thrust
constant was improved by 6.52% and 4.08%, and the amount of heat
generation was reduced by 11.87% and 7.69%.

[0055] Exposure apparatus 10 structured using linear motor 80 designed and
manufactured in the manner described above will be described.

[0056] FIG. 6 shows a schematic configuration of exposure apparatus 10
related to the present embodiment. Exposure apparatus 10 is a scanning
type exposure apparatus for liquid crystals used to transfer a pattern of
a reticle serving as a mask onto a glass plate for liquid crystals
serving as a substrate, using a step-and-scan method.

[0057] Exposure apparatus 10 is equipped with an illumination system 12, a
reticle stage device 14, a plate stage device 16, a projection optical
system which is not shown, a main section column 18 in which the
projection optical system is provided and the like.

[0058] Main section column 18 is structured from a surface plate 24
horizontally held via a plurality of (in this case, four) vibration
isolation pads 22 on the upper surface of a base frame (frame caster) 20
mounted on an installation floor, a first column 26 fixed on surface
plate 24, a second column which is not shown provided on the first column
26 and the like.

[0059] Of the sections, surface plate 24 structures a base of a plate
stage which will be described later on, and a movement plane 24a of the
plate stage is formed on the upper surface of surface plate 24.

[0060] In the first column 26, the projection optical system which is not
shown is held with the optical axis direction serving as a Z-axis
direction. As the projection optical system, a double telecentric
dioptric system is used here that has a projection magnification, for
example, of equal magnification.

[0061] The second column is fixed to the upper surface of the first column
26 in a state surrounding the projection optical system, and on the
second column, a reticle stage base 28 shown in FIG. 6 is fixed
horizontally. A movement plane 28a of a reticle stage RST is formed on
the upper surface of reticle stage base 28.

[0062] Vibration from the installation floor to main section column 18
structured in the manner described above is insulated at the micro-g
level by vibration isolation pads 22.

[0063] Illumination system 12 is structured with a light source unit, a
shutter, a secondary light source forming optical system, a beam
splitter, a condensing lens system, a reticle blind, an image-forming
lens system and the like (each of which are not shown) as disclosed in,
for example, Kokai (Japanese Unexamined Patent Application Publication)
No. 9-320956, and illuminates a rectangular shaped (or an arc shaped)
illumination area on reticle R (refer to FIG. 7) held on reticle stage
RST with a uniform illuminance. Illumination system 12, as shown in FIG.
6, is supported on the upper part of reaction force cancelling frames 40A
and 40B serving as a pair of holding members provided separately from
main section column 18, via a pair of support members 13A and 13B,
respectively. The lower ends of reaction force cancelling frames 40A and
40B are connected to the installation floor at the sides of base frame
20.

[0065] More particularly, a plurality of air pads which are not shown are
placed on the lower surface of reticle stage RST, and these air pads
support reticle stage RST by levitation via a predetermined clearance
with respect to movement plane 28a. In the center of reticle stage RST, a
recess section 15 having a rectangular sectional shape is formed, and
reticle R is made to be fixed to the inner bottom section of recess
section 15 by vacuum suction and the like. In the inner bottom section
(the rear surface side of reticle R) of recess section 15, a rectangular
opening (omitted in drawings) is formed which forms a path of the
illumination light.

[0066] Linear motor 30 is placed above reticle stage base 28 (refer to
FIG. 6), and is structured from a stator (magneto stator) 30A made up of
a magnetic pole unit which has a U-shaped cross-section and extends in a
scanning direction (in this case, a Y-axis direction), and a mover
(rotor) 30B made up of an armature unit which is integrally fixed to a
side surface on one side in the X direction (-X side) of reticle stage
RST. Stator 30A is actually fixed to the tip of a protruding portion on
the upper part of reaction force cancelling frame 40A.

[0067] Linear motor 32, as shown in FIG. 7, is placed above reticle stage
base 28 (refer to FIG. 6), and is structured from a stator (magneto
stator) 32A made up of a magnetic pole unit which has a U-shaped
cross-section and extends in the Y-axis direction, and a mover (rotor)
32B made up of an armature unit which is integrally fixed to a side
surface on the other side in the X direction (+X side) of reticle stage
RST. Stator 32A is actually fixed to the tip of a protruding portion on
the upper part of reaction force cancelling frame 408.

[0068] As linear motors 30 and 32, linear motors are used that employ a
driving method using the Lorentz force (electromagnetic force) whose
structures are similar to linear motor 80 previously described. Magnetic
pole units (stators 30A and 32A) and armature units (movers 30B and 32B)
of linear motors 30 and 32 correspond to magnet units 80B1 and
80B2 and coil unit BOA of linear motor 80, respectively. However,
linear motors 30 and 32 are moving-coil type motors, and the length of
the magnetic pole unit and the driving direction (Y-axis direction) is
shorter than the armature unit. Besides this point, linear motors 30 and
32 are structured in a similar manner as linear motor 80.

[0069] As described in detail so far, according to linear motor 80 of the
present embodiment, its design method, and its manufacturing method, the
magnetic field induced by the plurality of magnets Mij (i=1 to 5,
j=1 to 8) included in magnet units 80B1 and 80B2 which are
arranged corresponding to coil unit 80A is analyzed, and based on the
results of the analysis, the distribution is decided of the elements
which improves the coercivity inside each magnet, and based on the
distribution, each of the plurality of magnets are structured. This makes
it possible to realize a permanent magnet having strong magnetic force
and high heat-resisting performance whose residual magnetic flux density
and coercivity are both improved, using a small amount of an element
which improves coercivity. And, by designing a magnet unit using the
permanent magnet, and a motor using the magnet unit, it becomes possible
to design and manufacture a motor with high performance that has a large
driving force and is drivable at a high speed.

[0070] Further, reticle stage device 14 of the present embodiment uses
linear motors 30 and 32 structured in a similar manner as linear motor
80, as a driving source. By this arrangement, a stage device can be
obtained with high performance that can drive reticle stage RST at a high
speed.

[0071] Further, exposure apparatus 10 of the present embodiment is
equipped with reticle stage device 14 which uses linear motors 30 and 32
having a structure similar to linear motor 80. By this arrangement, an
exposure apparatus can be obtained which drives a mask at a high speed
and has a high throughput.

[0072] Incidentally, while linear motors 30 and 32 structured similar to
linear motor 80 of the present invention were used as the driving source
of reticle stage RST in reticle stage device 14 and exposure apparatus 10
of the present embodiment, linear motors 30 and 32 can also be used as
the driving source of plate stage PST in plate stage device 16.

[0073] Further, in the above embodiment, while the scanning type exposure
apparatus for liquid crystals equipped with linear motors structured
similar to linear motor 80 was described, besides such apparatuses, it is
a matter of course that the linear motor structured similar to linear
motor 80 and the stage device equipped with such linear motor can also be
applied in a similar manner to a scanning stepper used when manufacturing
semiconductor devices. Further, the present embodiment can also be
suitably applied, as a matter of course, to exposure apparatuses like a
stationary type exposure apparatus such as a projection exposure
apparatus (a so-called stepper) and the like using a step-and-repeat
method, or to an electron beam exposure apparatus (EB exposure
apparatus), or also to a laser repair apparatus or other apparatuses
equipped with an XY stage.

[0074] Further, the design method and manufacturing method of linear motor
80 in the above embodiment is not limited to linear motors, and can also
be used in rotary motors and planar motors.

[0075] Further, linear motor 80 of the above embodiment is not limited to
usage in stage devices and exposure apparatuses, and can also be suitably
used in linear motor cars, electric cars, hybrid cars and the like, in
motors used in a high temperature environment.

[0076] Incidentally, the disclosures of all the U.S. patent application
Publications and the U.S. patents that are cited in the description so
far related to exposure apparatuses and the like are each incorporated
herein by reference.

[0077] While the above-described embodiment of the present invention is
the presently preferred embodiment thereof, those skilled in the art of
lithography systems will readily recognize that numerous additions,
modifications, and substitutions may be made to the above-described
embodiment without departing from the spirit and scope thereof. It is
intended that all such modifications, additions, and substitutions fall
within the scope of the present invention, which is best defined by the
claims appended below.